The invention relates to an enclosure of a loudspeaker that preserves the bandwidth and output efficiency, naturalness and tonality of presentation.
A loudspeaker is a final element in a chain between a person and the sound that person desires to hear. As such, a loudspeaker must overcome many limitations to produce even reasonable musical fidelity. A loudspeaker transforms an incoming electrical signal to an acoustical signal that is processed by one""s ears and brain. The human ear is capable of receiving and interpreting signals over a wide range of frequencies, 20 to 20,000 Hertz (Hz). For a loudspeaker to sound natural, it must faithfully reproduce signals throughout this entire range. The major problem facing every loudspeaker designer is that the brain is an extremely sensitive instrument and has an uncanny ability to distinguish between the sound produced by a loudspeaker and that of the original instrument. The designer is also faced with having little or no control over the environment into which the loudspeaker will ultimately be placed. A loudspeaker normally comes in two units which can be placed anywhere in space at the discretion of the owner or listener.
Most speakers today typically comprise of two or more drivers which reproduce differing segments of the frequency spectrum; a crossover which splits up incoming frequencies and sends each select portion to an appropriately designed driver; and, a speaker enclosure which is a key element in a speaker""s sonic signature, and without which the bass frequencies will not be reproduced. This invention, however, is directed to an enclosure housing of what is known as a xe2x80x9cfull range driverxe2x80x9d, wherein there is just one driver and no crossovers. A full range driver means that it reproduces the entire audible range of frequency.
The preferred driver used for the claimed invention is the full range LOWTHER driver made commercially available by the LOWTHER Loudspeaker Systems, Kent, England such as the LOWTHER Dx, C and A series. This driver has a manufacturer claimed frequency response of 30 Hz-22 KHz, a sensitivity of 97 db/w/m (decibel/watt/meter) which when attached to the claimed enclosure goes well over 100 db/w/m and utilizes an ultra-light paper cone that gives it very high response speed which translate into crisper, clearer sound reproduction. The basic principle of operation involves sending a signal from a system""s amplifier through a speaker""s voice coil, a thin cylindrical wound wire which is attached to a thin cylinder connected to the speaker""s cone or dome. This voice coil is suspended in a magnetic field wherein a signal current in the suspended coil creates another magnetic field that interacts with the already existing field, causing the coil and the cone attached to it to vibrate. This vibration produces the sound. The LOWTHER driver used in conjunction with the claimed enclosure, as stated above, is a crossoverless loudspeaker. There are no electronics in the signal path between the amplifier and the transducer, also known as the driver, because it uses a single, full range voice coil driver which reproduces the entire aural spectrum. The claimed invention also improves on the LOWTHER driver by adding a third cone between the original two cones of the series of LOWTHER drivers used herein. As purchased, the LOWTHER full-range driver forrows a dual-cone, single voice typology, that is, there is a main cone and a smaller cone, commonly called a whizzer cone, that attaches concentrically to the main cone both of which are connected to a single voice coil. A third cone is proposed herein because most drivers with this dual cone configuration suffer from an elevated, meaning too much energy, in the upper midrange to lower treble frequencies (between 2 khz and 8 khz). This elevated energy is believed to be due to the waves produced by the main cone interacting or intermodulating with the waves produced by the whizzer cone. By introducing another cone in between these two cones, intermodulation does not occur specially in this crucial region. A loudspeaker""s enclosure has a tremendous influence on the reproduced sound. Vibrations in an enclosure or cabinet combine with the driver""s output to produce the sound heard by the listener. A poorly designed cabinet enclosing the finest drivers will produce a mediocre speaker/loudspeaker at best. The fundamental function of the enclosure is to deal with the rear or back wave of the driver. Rear wave and back wave are interchangeably used herein. The driver is a diaphragm that moves forward and backwards when fed with an electrical signal. Therefore, the rear wave produced is identical to the front wave, except that it is phase-reversed by 180 degrees. The enclosure needs to either deaden and absorb the rear wave or it needs to alter the rear wave in such a manner that cancellations between the front and rear waves do not occur. Cancellations limits the bandwidth and output efficiency of the driver. The environment around the driver is also important for the speed, detail, transparency and soundstaging characteristics of the loudspeaker. Consequently, the present invention also addresses the volume of space directly behind the driver but before the labyrinth, the pathway through which the sound waves travel before it exits to the outside environment. The volume of space directly behind the driver is referred to herein as the compression chamber. The volumetric proportions and geometric configuration of the compression chamber is crucial to the quality of the sound produced. The claimed invention addresses the geometric configuration of the compression chamber. When a rear wave from the driver first enters the compression chamber before exiting through an opening referred to herein as throat, the waves hit the surface facing it. If this surface is flat, the rear waves will be reflected back to the driver resulting in loss of sound clarity. The claimed invention designed a compression chamber having a cylindrical cross section to address this. The compression chamber holds the driver in one end with the other end facing a curved surface sloping down at approximately 45 degrees from the longitudinal axis of the cylinder, to direct all sound waves down into the labyrinth instead of being reflected back to the driver. Additionally, the materials from which an enclosure is built is also important because an understanding of the effect of vibrations on the surface of the material makes the designer able to correlate these with the sounds they produce.
There are many types of enclosures, most of which try to cancel out, enclose or deaden the rear waves. The claimed enclosure is a xe2x80x9chorn-loadedxe2x80x9d enclosure. Unlike the other enclosures that try to cancel or deaden the rear or back wave, this type of enclosure uses the back waves to the fullest, in a controlled manner depending upon the basic performance characteristics of the driver used. With LOWTHER drivers, the bass frequencies are channeled through the rear such that these are actually amplified instead of deadened when it comes out of the openings in the enclosure. While adopting the principles of a horn-loaded enclosure, the claimed invention did away with the traditional horn-load design principles and geometries. Traditional horn loaded enclosure uses flat sided boxes or enclosures which induces various colorations or sound distortion caused by a series of resonances produced by the reflection of the sound waves. The parallel-sided box which is the most common enclosure configuration, is prone to several deficiencies both as a result of the back wave acting on it internally and the front waves reflecting off its front external surface. Both these phenomena contribute to the xe2x80x9cmuddyingxe2x80x9d or distortion of the reproduced sound. These colorations are usually mollified but not eliminated by the use of bracing, damping or absorbing materials and massively heavy enclosures. The claimed invention uses several curved elements in the enclosure to eliminate coloration instead of ameliorating a created coloration.
It is an object of this invention to provide an enclosure that is designed to avoid coloration by eliminating completely any back wave reflections re-impacting the driver.
It is also an object of this invention to provide an enclosure that eliminates standing waves within the enclosure, thereby preventing box coloration.
It is also an object of this invention to provide an enclosure design that eliminates performance degrading baffle reflections and edge diffraction.
It is a further object of this invention to provide an enclosure which minimizes secondary box/enclosure/cabinet vibrations.
It is also a further object of the invention to improve the current two-cone full range drivers for better quality sound reproduction.
The present loudspeaker enclosure invention overcomes the problems of conventional horn-loaded loudspeakers such as coloration by eliminating standing sound waves within the enclosure and reflected sound waves off the enclosure re-impacting the driver; baffle reflection by having a curved front baffle surface; and, secondary cabinet vibration.
The loudspeaker enclosure meeting the objects of the invention is an assembly comprising of a hollow semicircularly curved casing having a cylindrical top, the cylindrical top having an open front end for introducing a driver thereto and a back end connecting to a first end of a sloping back semicircular side, the back semicircular side having a second end connected to a first end of a semicircular bottom surface, the semicircular bottom surface having a second end connected to a first end of a front semicircular side, the front semicircular side having a second end connecting to the front end of the cylindrical top thereby forming a semicircular front baffle of the enclosure; a series of interconnected flat baffles forming an internal baffle placed inside the hollow semicircularly curved casing, the series of flat baffles peripherally bordered by the hollow semicircularly curved casing and enclosed with side panels forming a labyrinth, an enclosed circuitous pathway of a constantly increasing cross section, the labyrinth subsequently splitting and terminating into an exit port for each split pathway, the side panels together with the hollow semicircularly curved casing forming the enclosure""s external walls; a compression chamber inside the cylindrical top of the semicircularly curved casing behind the driver, the compression chamber having a back open end facing the sloping back semicircular side to allow sound waves coming from the driver to travel down the labyrinth and prevent back waves from reflecting back to the driver; and, a base unit for holding and stabilizing the enclosure. The series of flat baffles are typically interconnected by gluing the individual baffles to each other to form the internal baffle of the enclosure which is in turn connected in an air tight manner to the side panels and the semicircularly curved casing by use of gaskets and sealants. The loudspeaker enclosure is assembled with the use of tie rods, tie rod cap nuts, gaskets and washers and is leveled with level adjuster spike and adjustable top bolts.
The invention also proposes the addition of an add-on cone to stock LOWTHER drivers to ameliorate certain energy peaks produced by the LOWTHER driver in the region between 2.5 kHz to 8 kHz.